CN105022235A - Manufacture method of extreme ultraviolet source collecting mirror with half-wave zone structure - Google Patents

Abstract

The invention provides a manufacture method of an extreme ultraviolet source collecting mirror with a half-wave zone structure, and relates to the field of the extreme ultraviolet source collecting mirrors. The manufacture method of the invention solves the problems that the existing method is high in cost, and an unnecessary pattern error will generate simultaneously. The method comprises the steps as follows: substrate cleaning, gluing, exposing, baking, developing, etching, removing of photoresist and film plating. In the process of exposing, an exposure source, a beam expander, a source collecting mirror, a curved semi-reflecting and semi-transmitting lens and a curved reflector are arranged along an optical axis in turn, wherein the focal points of the curved semi-reflecting and semi-transmitting lens and the curved reflector coincide with two focal points of an ellipsoid where an elliptical surface of the source collecting mirror is located; the focal length of the ellipsoid where the elliptical surface of the source collecting mirror is located equals to odd times of one quarter of a laser wavelength output by the exposure source; and interferometric fringes are formed on the elliptical surface of the source collecting mirror through the interference of two coherent point light sources to enable the coating to sense light to finish the exposure. The manufacture method of the invention is simple in technology, and low in cost, and there is no error brought by manufacturing a mask plate, thereby improving spectrum purification efficiency of the half-wave zone structure.

Description

The EUV light source with half-wave zone structure collects the method for making of mirror

Technical field

The present invention relates to extreme ultraviolet (Extreme Ultraviolet, EUV) source-collector mirror technical field, be specifically related to the method for making that a kind of EUV light source with half-wave zone structure collects mirror.

Background technology

In recent years, extreme ultraviolet photolithographic (EUV Lithograph, EUVL) technology is developed widely.EUVL uses 13.5nm wavelength light source as service band, can realize tens nanometers, the lithographic line width of even a few nanometer, and then increases the integrated level of integrated circuit greatly, is extremely important to the miniaturization of electronic equipment, low-power consumption development.

Extreme ultraviolet photolithographic equipment is generally made up of EUV light source, illuminator and projection objective.Wherein, EUV light source provides the extreme ultraviolet radiation needed for photolithographic exposure.Having high-power is the precondition realizing extreme ultraviolet photolithographic volume production with EUV light source that is high-purity spectrum, is also one of difficult point of current extreme ultraviolet lithography.

At present, extreme ultraviolet radiation can be produced by synchrotron radiation and high-temperature high-density plasma radiation.In Practical Project, the EUV light source based on high-temperature high-density plasma radiation more has practical value.According to the different excitation principles of plasma, EUV light source can be divided into again discharge plasma (Discharge ProducedPlasma, DPP) light source and laser plasma (Laser Produced Plasma, LPP) light source two type.The former utilizes interelectrode effluve activated plasma, but due to plasma distance electrode comparatively near, inevitably fire damage is produced to electrode and fragment clashes into, limits the application of DPP light source.The latter utilizes driving laser to bombard target activated plasma, can realize high-power, stable extreme ultraviolet and export, in recent years by research and apply widely.

The LPP light source being applied to extreme ultraviolet lithography is generally made up of driving light source, target system and collection system.Wherein, driving light source generally selects the gas laser that can realize high-power output, as CO ₂laser instrument etc.; Target system is made up of target and target transport sector, and common target has Sn droplet target, Xe gas target etc.; Collection system is the extreme ultraviolet light beam that collection plasma resonance goes out, and is converged to the device of intermediate focus (Intermediate Focus, IF), and the general ellipsoid being coated with extreme ultraviolet reflectance coating that uses collects mirror to realize this function.Meanwhile, in order to reduce the damage of fragment to illuminator in extreme ultraviolet photolithographic equipment, improving the spectral purity of emergent light, also can arrange in LPP light source except fragment system and spectrum purification system etc.In LPP light source, the light collecting mirror collection through ellipsoid comprises extreme ultraviolet, deep UV (ultraviolet light) (DeepUltraviolet, DUV) and the infrared light (Infrared, IR) from driving light source.Wherein, the thermal effect that infrared light produces understands the serviceable life of optical element in serious curtailment extreme ultraviolet photolithographic equipment.To this, researchist proposes multiple solution.

2014, the people such as Holland scholar Muharrem Bayraktar devise a kind of source-collector mirror (OPTICS EXPRESS with Fresnel half-wave zone structure, 22 (7), 8633-8639,2014), utilize zone plate principle to make infrared light " refocusing ", converge to the application point of driving light source and target system, achieve the suppression of exit end to infrared light, meanwhile, exciting of plasma can be promoted.This method is effectively novel, can also derive the design proposal that other EUV light sources with half-wave zone structure collect mirror simultaneously.

Collecting the making of mirror about this EUV light source with microstructures such as half-wave zones, is generally adopt projection lithography method: first, designs half-wave zone pattern, and be made into mask plate by calculating; Then use exposure light source to be irradiated the collection mirror scribbling photoresist by mask plate, make photoresist photosensitive, form half-wave zone pattern; Again through plated film or etching and wash the techniques such as glue and make the EUV light source with half-wave zone structure and collect mirror.Obviously, the half-wave zone pattern collected on mirror greatly depends on the quality of mask plate.This not only adds cost of manufacture, also can introduce unnecessary pattern errors simultaneously, reduce source efficiency.Diamond turning (Diamond Turning) method also can be used to make microstructure on collection mirror, but manufacturing procedure is complicated, fabrication cycle long, there is effective application that the factors such as error constrain this method.

In sum, in view of the EUV light source with half-wave zone structure collects the practical value of mirror, a kind of method that simple making accurately has the half-wave zone structure of spectrum purifying function on EUV light source collection mirror has important practical significance.

Summary of the invention

The cost that the method for collecting mirror to solve existing making EUV light source exists is high, also can introduce the problem of unnecessary pattern errors simultaneously, the invention provides the method for making that a kind of EUV light source with half-wave zone structure collects mirror, can collect at EUV light source half-wave zone structure mirror making there is spectrum purifying function simply accurately.

The technical scheme that the present invention adopts for technical solution problem is as follows:

The EUV light source with half-wave zone structure of the present invention collects the method for making of mirror, comprises the following steps:

Step one, substrate cleaning

Utilize supersonic wave cleaning machine to carry out Ultrasonic Cleaning, alcohol oven dry to source-collector mirror, remove surface contaminant;

Step 2, gluing

The material with function against corrosion can be produced under the ellipsoid of source-collector mirror is spin-coated on exposure light source irradiation, form coating;

Step 3, exposure

Build exposure light path: set gradually exposure light source, beam expander, source-collector mirror, curved surface half-reflecting half mirror and curved reflector along optical axis, the focus of described curved surface half-reflecting half mirror and the focus of curved reflector respectively with the first focal point F of the ellipsoid place ellipsoid of source-collector mirror ₁with the second focal point F ₂overlap, described curved surface half-reflecting half mirror and curved reflector all can reflect to form spherical wave to directional light, and the focal length of the ellipsoid place ellipsoid of described source-collector mirror equals the odd-multiple of the optical maser wavelength 1/4th that exposure light source exports;

Interfered by two coherent point light sources and form interference fringe on the ellipsoid of source-collector mirror, make the coating on ellipsoid photosensitive come exposure: the laser that described exposure light source exports forms parallel incident light after beam expander expands, incident light is radiated at curved surface half-reflecting half mirror surface through the through hole in the middle of source-collector mirror, described curved surface half-reflecting half mirror forms the first reflected light i.e. the first spherical wave to a part of reflected incident light, transmitted light is formed to the transmission of another part incident light and is radiated at curved mirror surfaces, described curved reflector reflects to form the second reflected light i.e. the second spherical wave to transmitted light, described first reflected light and the second reflected light are all radiated on the ellipsoid of source-collector mirror, first focal point F of the centre of sphere of described first spherical wave and the focus of curved surface half-reflecting half mirror, source-collector mirror ₁overlap, the second focal point F of the centre of sphere of described second spherical wave and the focus of curved reflector, source-collector mirror ₂overlap, described first spherical wave and the second spherical wave interfere formation interference fringe on the ellipsoid of source-collector mirror, make that the coating on ellipsoid is photosensitive completes exposure simultaneously,

Step 4, baking

Source-collector mirror after exposure is placed and toasts in an oven;

Step 5, development

Adopt solvent cleaning source-collector mirror, the coating of unexposed area on the ellipsoid of removal source-collector mirror;

Step 6, etching

Adopt etching liquid etch away sections substrate on the ellipsoid with the patterned source-collector mirror of half-wave, etch thicknesses is 1/4th of the optical maser wavelength that exposure light source exports;

Step 7, to remove photoresist

Coating on the ellipsoid utilizing equipment for burning-off photoresist by plasma to remove source-collector mirror after exposure, makes half-wave zone structure expose;

Step 8, plated film

The ellipsoid of source-collector mirror with half-wave zone structure is coated with one deck extreme ultraviolet reflectance coating, completes the making that the EUV light source with half-wave zone structure collects mirror.

Further, in step 2, can produce the material with function against corrosion under exposure light source irradiation is photosensitive material or sensible heat material.

Further, described sensible heat material, for adopting heat cross-linking Computer To Plate material, is made up of infrared absorbing dye, resol resin, novolac resin and salt.

Further, described curved surface half-reflecting half mirror is identical with Curved reflecting mirror structure, is a kind of by CO ₂the paraboloidal mirror that the material of laser-light transparent is made; Described curved surface half-reflecting half mirror surface is coated with part reflective semitransparent film, and described curved surface half-reflection and half-transmission aperture of mirror is greater than the diameter carrying out the directional light expanded through beam expander; Described curved mirror surfaces is coated with high-reflecting film.

Further, in step 4, baking condition is: toast 1min at 100 DEG C.

Further, the modes of emplacement of described curved surface half-reflecting half mirror and curved reflector has four kinds, is respectively: the first inside surface of curved surface half-reflecting half mirror is simultaneously relative with the ellipsoid of source-collector mirror with the second inside surface of curved reflector; First outside surface of curved surface half-reflecting half mirror is simultaneously relative with the ellipsoid of source-collector mirror with the second outside surface of curved reflector; First inside surface of curved surface half-reflecting half mirror is simultaneously relative with the ellipsoid of source-collector mirror with the second outside surface of curved reflector; First outside surface of curved surface half-reflecting half mirror is simultaneously relative with the ellipsoid of source-collector mirror with the second inside surface of curved reflector.

Further, described exposure light source adopts CO ₂laser instrument, CO ₂optical maser wavelength is 10.6 μm.

Further, dilute sodium silicate solution selected by described solvent.

Further, described etching liquid selects rare HNO ₃with the mixed solution of HF.

Further, described extreme ultraviolet reflectance coating is Mo/Si multilayer film, cycle 6.9nm, is made up of 40 ~ 50 cycles.

Further, step 9, detection is also comprised:

If A, B are two points on the ellipsoid of source-collector mirror, its mid point A is positioned at through hole center, and is positioned at the intersection of primary optical axis and ellipsoid, and some B is on ellipsoid, and some A does not overlap with some B;

When the ellipsoid of source-collector mirror has suitable half-wave zone structure, source-collector mirror by infrared light refocusing, thus realizes the spectrum purifying function at intermediate focus IF place, therefore, half-wave zone structure should be made to meet the reflector space of infrared light: path with path optical path difference be the odd-multiple of half-wavelength of the laser that exposure light source exports, shown in (1):

$\stackrel{\‾}{F_1{\mathrm{BF}}_1}-\stackrel{\‾}{F_1{\mathrm{AF}}_1}=(2n+1)\mathrm{\λ}$ \*MERGEFORMAT(1)

In formula (1), F ₁for the first focus of the ellipsoid at the ellipsoid place of source-collector mirror, λ is the optical maser wavelength that exposure light source exports, and n is natural number;

Two coherent point light sources lay respectively at the first focal point F ₁with the second focal point F ₂, two coherent point light sources form interference fringe on ellipsoid, and wherein bright fringes meets: path with path optical path difference be the integral multiple of wavelength of the laser that exposure light source exports, shown in (2):

$\stackrel{\‾}{F_{2}B}-\stackrel{\‾}{F_{1}B}=m\mathrm{\λ}$ \*MERGEFORMAT(2)

In formula (2), F ₂for the second focus of the ellipsoid at the ellipsoid place of source-collector mirror, optical maser wavelength that exposure light source exports that to be also the intermediate focus IF of exposure light source output terminal, λ be, m is natural number.

In the ellipsoid at the ellipsoid place of source-collector mirror, there is following geometric relationship: on the ellipsoid at the ellipsoid place of source-collector mirror o'clock to the first focal point F ₁, the second focal point F ₂the major axis of distance sum to be constant 2a, a the be ellipsoid at the ellipsoid place of source-collector mirror long, shown in (3):

$\stackrel{\‾}{F_{1}B}+\stackrel{\‾}{F_{2}B}=2a$ \*MERGEFORMAT(3)

In addition, also exist such as formula the relational expression shown in (4):

$\stackrel{\‾}{F_{1}A}=a-f$ \*MERGEFORMAT(4)

In formula (4), f is the focal length of the ellipsoid at the ellipsoid place of source-collector mirror;

Can be drawn by formula (1), formula (2), formula (3) and formula (4):

$\begin{array}{c}{\stackrel{\‾}{F_{1}BF}}_1-{\stackrel{\‾}{F_{1}AF}}_1=2\stackrel{\‾}{F_{1}B}-2\stackrel{\‾}{F_{1}A}\\ =(2a-m\mathrm{\λ})-2(a-f)\\ =2f-m\mathrm{\λ}\end{array}$ \*MERGEFORMAT(5)

Focal length due to the ellipsoid at the ellipsoid place of described source-collector mirror is the odd-multiple of the optical maser wavelength 1/4th that exposure light source exports, that is:

$f=(2l+1)\frac{\mathrm{\λ}}{4}$ \*MERGEFORMAT(6)

In formula (6), f is the focal length of the ellipsoid at the ellipsoid place of source-collector mirror, and λ is the optical maser wavelength that exposure light source exports, and l is natural number;

Then can be drawn by formula (5) and formula (6):

$\stackrel{\‾}{F_1{\mathrm{BF}}_1}-\stackrel{\‾}{F_1{\mathrm{AF}}_1}=\left(2\right(l-m)+1)\mathrm{\λ}$ \*MERGEFORMAT(7)

By the first focal point F in the ellipsoid at the ellipsoid place of described source-collector mirror ₁, the second focal point F ₂and the triangle Δ F that the some B on ellipsoid is formed ₁bF ₂in i.e. 2l+1 > 2m;

In sum, two coherent point light sources are utilized to interfere the candy strip constructed on the ellipsoid of source-collector mirror consistent with required half-wave zone structure plan.

The invention has the beneficial effects as follows:

1, the present invention is exposed by the interference fringe of two pointolites, instead of making and the use of mask plate in existing photoetching process, and do not need to use illuminator in projection lithography and projection objective system etc., simplify manufacture craft, reduce cost of manufacture simultaneously.

2, the interference fringe formed due to the exposure light path that uses in the present invention and required half-wave zone structure completely the same, do not have mask plate to make the error introduced, thus greatly can improve the spectrum purification efficiency that EUV light source collects half-wave zone structure in mirror system.

3, the present invention utilizes principle of interference, half-wave zone pattern can be constructed accurately and effectively on the ellipsoid of source-collector mirror, be combined the half-wave zone structure can prepared and there is spectrum purifying function with similar photoetching process, and improve the spectrum purification efficiency of half-wave zone structure.

Accompanying drawing explanation

Fig. 1 is the structural representation that typical EUV light source collects mirror.

Fig. 2 is two point sotuce exposure light path schematic diagram.

Fig. 3 is the effect schematic diagram of curved surface half-reflecting half mirror (curved reflector) inside surface to light.

Fig. 4 is the effect schematic diagram of curved surface half-reflecting half mirror (curved reflector) outside surface to light.

In Fig. 1: 1, source-collector mirror, 2, ellipsoid, 3, primary optical axis, 4, curved surface half-reflecting half mirror, 5, curved reflector, 6, exposure light source, 7, beam expander, 8, through hole, 9, the first inside surface, 9 ', second inside surface, the 10, first outside surface, the 10 ', second outside surface, 11, incident light, 11 ', transmitted light, 12, incident light cophasal surface, 12 ', transmitted light cophasal surface, 13, the first reflected light, 13 ', second reflected light, the 14, first reflected light cophasal surface, the 14 ', second reflected light cophasal surface.

Embodiment

Below in conjunction with accompanying drawing, the present invention is described in further details.

The EUV light source with half-wave zone structure of the present invention collects the method for making of mirror, realizes especially by following steps:

Step one, substrate cleaning

Utilize supersonic wave cleaning machine to carry out Ultrasonic Cleaning, alcohol oven dry etc. to source-collector mirror 1, remove surface contaminant.

In method of the present invention, use existing typical source-collector mirror 1 as substrate, its structure as depicted in figs. 1 and 2.The minute surface of source-collector mirror 1 is ellipsoid 2, and ellipsoid 2 is through design processing, and Frequency Surface roughness is about 0.1nm.The center of source-collector mirror 1 is through hole 8.F ₁, F ₂for the first focus application point of driving light source and target (when namely source-collector mirror 1 works) and second focus (intermediate focus IF) of the ellipsoid 2 place ellipsoid of source-collector mirror 1, the first focal point F ₁with the second focal point F ₂all be positioned on the primary optical axis 3 of source-collector mirror 1.A, B are two points on the ellipsoid 2 of source-collector mirror 1, and its mid point A is positioned at through hole 8 center, and are positioned at primary optical axis 3 and the intersection of ellipsoid 2, put B on ellipsoid 2, and some A do not overlap with some B.Source-collector mirror 1 diameter 600mm, thickness 30mm, effectively collecting aperture is 5sr, and center is the through hole 8 of diameter 50mm.The glass material that source-collector mirror 1 selects ULE etc. to have ultra-low thermal expansion is made.

Step 2, gluing

Photosensitive material (negative photoresist of the functionally similar photoetching process use) spin coating on the ellipsoid 2 of source-collector mirror 1 with function against corrosion can be produced under being used in exposure light source 6 irradiation and form light sensitive layer;

Or, sensible heat material (negative photoresist of the functionally similar photoetching process use) spin coating on the ellipsoid 2 of source-collector mirror 1 with function against corrosion can be produced under being used in exposure light source 6 irradiation and form sensible heat coating;

On the ellipsoid 2 of source-collector mirror 1 formed range of coat thicknesses for: spin coating thickness is relevant with the optical maser wavelength that used material category, exposure light source 6 export, generally zero point several microns to several microns.

In present embodiment, the said sensible heat material with function against corrosion can adopt heat cross-linking Computer To Plate material, is generally made up of infrared absorbing dye, resol resin, novolac resin and salt etc.

Step 3, exposure

By building exposure light path, utilize simultaneously two coherent point light sources interfere on the ellipsoid 2 of source-collector mirror 1, form interference fringe, and make the coating on ellipsoid 2 photosensitive come exposing operation.

The exposure light path built as shown in Figure 2, comprise exposure light source 6, beam expander 7, source-collector mirror 1, curved surface half-reflecting half mirror 4 and curved reflector 5, exposure light source 6, beam expander 7, curved surface half-reflecting half mirror 4 and curved reflector 5 are positioned on the primary optical axis 3 of source-collector mirror 1 successively, namely the main shaft of exposure light source 6, beam expander 7, source-collector mirror 1, curved surface half-reflecting half mirror 4 and curved reflector 5 on the same line, and curved surface half-reflecting half mirror 4 is near the ellipsoid 2 of source-collector mirror 1.The focal length of the ellipsoid 2 place ellipsoid of source-collector mirror 1 equals the odd-multiple of the optical maser wavelength 1/4th that exposure light source 6 exports.

In present embodiment, said curved surface half-reflecting half mirror 4 be a kind of by Si etc. to CO ₂the paraboloidal mirror that the material of laser-light transparent is made, surface is coated with part reflective semitransparent film.Curved surface half-reflecting half mirror 4 bore is slightly larger than the diameter (about 5mm) carrying out the directional light expanded through beam expander 7.The focus of curved surface half-reflecting half mirror 4 and the first focal point F of source-collector mirror 1 ₁overlap.By placing first focal point F of curved surface half-reflecting half mirror 4 at source-collector mirror 1 ₁place's formation pointolite.

In present embodiment, said curved reflector 5 has identical structure with curved surface half-reflecting half mirror 4, said curved reflector 5 be also a kind of by Si etc. to CO ₂the paraboloidal mirror that the material of laser-light transparent is made, surface is coated with high-reflecting film.The focus of curved reflector 5 and the second focal point F of source-collector mirror 1 ₂overlap.By placing second focal point F of curved reflector 5 at source-collector mirror 1 ₂place forms another pointolite.

In present embodiment, the driving light source used when said exposure light source 6 works with EUV light source is consistent, generally adopts CO ₂laser instrument, CO ₂optical maser wavelength is 10.6 μm.When exposure light source 6 adopts CO ₂during laser instrument, in step 2, the thickness of the coating that the ellipsoid 2 of source-collector mirror 1 is formed is about several microns.

In present embodiment, can normally work to make curved surface half-reflecting half mirror 4 and curved reflector 5, the laser beam expanding that exported by exposure light source 6 of beam expander 7 is used to be about 5mm to diameter at exposure light source 6 output terminal, formation diameter about 5mm and the incident light 11 be parallel to each other.

In present embodiment, curved surface half-reflecting half mirror 4 has four kinds with the modes of emplacement of curved reflector 5, is respectively: the first inside surface 9 of curved surface half-reflecting half mirror 4 is simultaneously relative with the ellipsoid 2 of source-collector mirror 1 with the second inside surface 9 ' of curved reflector 5; First outside surface 10 of curved surface half-reflecting half mirror 4 is simultaneously relative with the ellipsoid 2 of source-collector mirror 1 with the second outside surface 10 ' of curved reflector 5; First inside surface 9 of curved surface half-reflecting half mirror 4 is simultaneously relative with the ellipsoid 2 of source-collector mirror 1 with the second outside surface 10 ' of curved reflector 5; First outside surface 10 of curved surface half-reflecting half mirror 4 is simultaneously relative with the ellipsoid 2 of source-collector mirror 1 with the second inside surface 9 ' of curved reflector 5.

Below illustrate.First inside surface 9 of curved surface half-reflecting half mirror 4 is simultaneously relative with the ellipsoid 2 of source-collector mirror 1 with the second inside surface 9 ' of curved reflector 5.The laser that exposure light source 6 exports is after beam expander 7 expands, form the directional light of diameter about 5mm, namely the incident light 11 be parallel to each other, as shown in Figure 3, more incident light 11 forms incident light cophasal surface 12, incident light 11 is radiated on the first inside surface 9 of curved surface half-reflecting half mirror 4 through the through hole 8 in the middle of source-collector mirror 1, curved surface half-reflecting half mirror 4 surface is coated with part reflective semitransparent film, the incident light 11 of curved surface half-reflecting half mirror 4 to a part reflects to form the first reflected light 13 i.e. the first spherical wave, multi beam first reflected light 13 forms the first reflected light cophasal surface 14, first reflected light 13 is radiated on the ellipsoid 2 of source-collector mirror 1, the centre of sphere of said first spherical wave and the focus of curved surface half-reflecting half mirror 4, first focal point F of source-collector mirror 1 ₁overlap, the incident light 11 of curved surface half-reflecting half mirror 4 pairs of another part carries out transmission and forms transmitted light 11 ', transmitted light 11 ' is radiated on the second inside surface 9 ' of the curved reflector 5 being placed in curved surface half-reflecting half mirror 4 rear, curved reflector 5 surface is coated with high-reflecting film, curved reflector 5 pairs of transmitted lights 11 ' reflect to form the second reflected light 13 ' i.e. the second spherical wave, multi beam second reflected light 13 ' forms the second reflected light cophasal surface 14 ', second reflected light 13 ' is radiated on the ellipsoid 2 of source-collector mirror 1, the centre of sphere of said second spherical wave and the focus of curved reflector 5, second focal point F of source-collector mirror 1 ₂overlap, first spherical wave and the second spherical wave interfere and form interference fringe on the ellipsoid 2 of source-collector mirror 1, make the coating on ellipsoid 2 photosensitive, complete exposing operation.

First outside surface 10 of curved surface half-reflecting half mirror 4 is simultaneously relative with the ellipsoid 2 of source-collector mirror 1 with the second outside surface 10 ' of curved reflector 5.The laser that exposure light source 6 exports is after beam expander 7 expands, form the directional light of diameter about 5mm, namely the incident light 11 be parallel to each other, as shown in Figure 4, more incident light 11 forms incident light cophasal surface 12, incident light 11 is radiated on the first outside surface 10 of curved surface half-reflecting half mirror 4 through the through hole 8 in the middle of source-collector mirror 1, curved surface half-reflecting half mirror 4 surface is coated with part reflective semitransparent film, the incident light 11 of curved surface half-reflecting half mirror 4 to a part reflects to form the first reflected light 13 i.e. the first spherical wave, multi beam first reflected light 13 forms the first reflected light cophasal surface 14, first reflected light 13 is radiated on the ellipsoid 2 of source-collector mirror 1, the centre of sphere of said first spherical wave and the focus of curved surface half-reflecting half mirror 4, first focal point F of source-collector mirror 1 ₁overlap, the incident light 11 of curved surface half-reflecting half mirror 4 pairs of another part carries out transmission and forms transmitted light 11 ', transmitted light 11 ' is radiated on the second outside surface 10 ' of the curved reflector 5 being placed in curved surface half-reflecting half mirror 4 rear, curved reflector 5 surface is coated with high-reflecting film, curved reflector 5 pairs of transmitted lights 11 ' reflect to form the second reflected light 13 ' i.e. the second spherical wave, multi beam second reflected light 13 ' forms the second reflected light cophasal surface 14 ', second reflected light 13 ' is radiated on the ellipsoid 2 of source-collector mirror 1, the centre of sphere of said second spherical wave and the focus of curved reflector 5, second focal point F of source-collector mirror 1 ₂overlap, first spherical wave and the second spherical wave interfere and form interference fringe on the ellipsoid 2 of source-collector mirror 1, make the coating on ellipsoid 2 photosensitive, complete exposing operation.

Step 4, baking

Source-collector mirror 1 after overexposure is placed in an oven, at 100 DEG C, toasts about 1min.

Step 5, development

Utilize solvent cleaning source-collector mirror 1, the coating of unexposed area on the ellipsoid 2 of removal source-collector mirror 1.Solvent for use can select dilute sodium silicate solution etc.

Step 6, etching

After development, utilize etching liquid etch away sections substrate on the ellipsoid 2 with the patterned source-collector mirror 1 of half-wave.Etch thicknesses is 1/4th of the optical maser wavelength that exposure light source 6 exports, and according to principle of interference, this etch thicknesses can realize the maximum contrast of infrared light reflection light.Etching liquid used can select rare HNO ₃with the mixed solution of HF.

Step 7, to remove photoresist

Utilize equipment for burning-off photoresist by plasma, the coating on the ellipsoid 2 of removal source-collector mirror 1 after exposure, makes half-wave zone structure expose.

Step 8, plated film

The ellipsoid 2 of source-collector mirror 1 with half-wave zone structure is coated with one deck extreme ultraviolet reflectance coating, the making that the EUV light source with half-wave zone structure collects mirror can be completed.Said extreme ultraviolet reflectance coating, is generally Mo/Si multilayer film, cycle 6.9nm, is generally made up of 40 ~ 50 cycles.

Step 9, detection

According to Muharrem Bayraktar at document (OPTICS EXPRESS, 22 (7), 8633-8639,2014) discussion in, when the ellipsoid 2 of source-collector mirror 1 has suitable half-wave zone structure, source-collector mirror 1 by infrared light " refocusing ", thus realizes intermediate focus IF place (i.e. the second focal point F ₂place) spectrum purifying function.Therefore, as shown in Figure 1, half-wave zone structure should be made to meet the reflector space of infrared light: path with path optical path difference be the odd-multiple of half-wavelength of the laser that exposure light source 6 exports, shown in (1):

$\stackrel{\‾}{F_1{\mathrm{BF}}_1}-\stackrel{\‾}{F_1{\mathrm{AF}}_1}=(2n+1)\mathrm{\λ}$ \*MERGEFORMAT(1)

In formula (1), F ₁for the first focus of the ellipsoid at ellipsoid 2 place of source-collector mirror 1, being also the application point of source-collector mirror 1 driving light source and target when working, is the source point of extreme ultraviolet radiation; λ is the optical maser wavelength that exposure light source 6 exports; N is natural number.

The present invention utilizes two coherent point light sources to interfere and constructs candy strip at ellipsoid 2.As shown in Figure 1, two coherent point light sources lay respectively at the first focal point F ₁with the second focal point F ₂.Two coherent point light sources form interference fringe on ellipsoid 2, and wherein bright fringes meets: path with path optical path difference be the integral multiple of wavelength of the laser that exposure light source 6 exports, shown in (2):

$\stackrel{\‾}{F_{2}B}-\stackrel{\‾}{F_{1}B}=m\mathrm{\λ}$ \*MERGEFORMAT(2)

In formula (2), F ₂for the second focus of the ellipsoid at ellipsoid 2 place of source-collector mirror 1, be also the intermediate focus IF of exposure light source 6 output terminal; λ is the optical maser wavelength that exposure light source 6 exports; M is natural number.

In the ellipsoid at ellipsoid 2 place of source-collector mirror 1, also there is following geometric relationship: on the ellipsoid at ellipsoid 2 place of source-collector mirror 1 o'clock to the first focal point F ₁, the second focal point F ₂the major axis of distance sum to be constant 2a, a the be ellipsoid at ellipsoid 2 place of source-collector mirror 1 long, shown in (3):

$\stackrel{\‾}{F_{1}B}+\stackrel{\‾}{F_{2}B}=2a$ \*MERGEFORMAT(3)

In addition, also exist such as formula the relational expression shown in (4):

$\stackrel{\‾}{F_{1}A}=a-f$ \*MERGEFORMAT(4)

In formula (4), f is the focal length of the ellipsoid at ellipsoid 2 place of source-collector mirror 1.

Can be drawn by formula (1), formula (2), formula (3) and formula (4):

$\begin{array}{c}{\stackrel{\‾}{F_{1}BF}}_1-{\stackrel{\‾}{F_{1}AF}}_1=2\stackrel{\‾}{F_{1}B}-2\stackrel{\‾}{F_{1}A}\\ =(2a-m\mathrm{\λ})-2(a-f)\\ =2f-m\mathrm{\λ}\end{array}$ \*MERGEFORMAT(5)

The focal length that the present invention proposes the ellipsoid 2 place ellipsoid of source-collector mirror 1 is especially the odd-multiple of the optical maser wavelength 1/4th that exposure light source 6 exports, that is:

$f=(2l+1)\frac{\mathrm{\λ}}{4}$ \*MERGEFORMAT(6)

In formula (6), f is the focal length of the ellipsoid at ellipsoid 2 place of source-collector mirror 1; λ is the optical maser wavelength that exposure light source 6 exports; L is natural number.

Then can be drawn by formula (5) and formula (6):

$\stackrel{\‾}{F_1{\mathrm{BF}}_1}-\stackrel{\‾}{F_1{\mathrm{AF}}_1}=\left(2\right(l-m)+1)\mathrm{\λ}$ \*MERGEFORMAT(7)

Further, as shown in Figure 1, it is evident that: by the first focal point F in the ellipsoid at ellipsoid 2 place of source-collector mirror 1 ₁, the second focal point F ₂and the triangle Δ F that the some B on ellipsoid 2 is formed ₁bF ₂in $\stackrel{\‾}{F_1{F}_2}>\stackrel{\‾}{F_{2}B}-\stackrel{\‾}{F_{1}B},$ I.e. 2l+1 > 2m.

In sum, the present invention utilizes two coherent point light sources to interfere the candy strip of structure on the ellipsoid 2 of source-collector mirror 1 consistent with required half-wave zone structure plan.

Claims (10)

1. the EUV light source with half-wave zone structure collects the method for making of mirror, it is characterized in that, comprises the following steps:

Step one, substrate cleaning

Utilize supersonic wave cleaning machine to carry out Ultrasonic Cleaning, alcohol oven dry to source-collector mirror (1), remove surface contaminant;

Step 2, gluing

The material with function against corrosion can be produced under the ellipsoid (2) of source-collector mirror (1) is spin-coated on exposure light source (6) irradiation, form coating;

Step 3, exposure

Build exposure light path: set gradually exposure light source (6), beam expander (7), source-collector mirror (1), curved surface half-reflecting half mirror (4) and curved reflector (5) along optical axis, the focus of described curved surface half-reflecting half mirror (4) and the focus of curved reflector (5) respectively with the first focal point F of ellipsoid (2) the place ellipsoid of source-collector mirror (1) ₁with the second focal point F ₂overlap, described curved surface half-reflecting half mirror (4) and curved reflector (5) all can reflect to form spherical wave to directional light, and the focal length of ellipsoid (2) the place ellipsoid of described source-collector mirror (1) equals the odd-multiple of the optical maser wavelength 1/4th that exposure light source (6) exports;

Interfered by two coherent point light sources and form interference fringe on the ellipsoid (2) of source-collector mirror (1), make the coating on ellipsoid (2) photosensitive come exposure: the incident light (11) that the laser that described exposure light source (6) exports formation after beam expander (7) expands is parallel, incident light (11) is radiated at curved surface half-reflecting half mirror (4) surface through the through hole (8) in the middle of source-collector mirror (1), described curved surface half-reflecting half mirror (4) reflects to form the first reflected light (13) i.e. the first spherical wave to a part of incident light (11), transmitted light (11 ') is formed to another part incident light (11) transmission and is radiated at curved reflector (5) surface, described curved reflector (5) reflects to form the second reflected light (13 ') i.e. the second spherical wave to transmitted light (11 '), described first reflected light (13) and the second reflected light (13 ') are all radiated on the ellipsoid (2) of source-collector mirror (1), first focal point F of the centre of sphere of described first spherical wave and the focus of curved surface half-reflecting half mirror (4), source-collector mirror (1) ₁overlap, the second focal point F of the centre of sphere of described second spherical wave and the focus of curved reflector (5), source-collector mirror (1) ₂overlap, described first spherical wave and the second spherical wave interfere formation interference fringe on the ellipsoid (2) of source-collector mirror (1), make that the coating on ellipsoid (2) is photosensitive completes exposure simultaneously,

Step 4, baking

Source-collector mirror (1) after exposure is placed and toasts in an oven;

Step 5, development

Adopt solvent cleaning source-collector mirror (1), remove the coating of the upper unexposed area of ellipsoid (2) of source-collector mirror (1);

Step 6, etching

Adopt etching liquid in the upper etch away sections substrate of the ellipsoid (2) with the patterned source-collector mirror (1) of half-wave, etch thicknesses is 1/4th of the optical maser wavelength that exposure light source (6) exports;

Step 7, to remove photoresist

Utilize equipment for burning-off photoresist by plasma to remove the upper coating after exposing of ellipsoid (2) of source-collector mirror (1), half-wave zone structure is exposed;

Step 8, plated film

The ellipsoid (2) of source-collector mirror (1) with half-wave zone structure is coated with one deck extreme ultraviolet reflectance coating, completes the making that the EUV light source with half-wave zone structure collects mirror.

2. method for making according to claim 1, is characterized in that, in step 2, can produce the material with function against corrosion under exposure light source (6) irradiation is photosensitive material or sensible heat material;

Described sensible heat material is heat cross-linking Computer To Plate material, is made up of infrared absorbing dye, resol resin, novolac resin and salt.

3. method for making according to claim 1, is characterized in that, described curved surface half-reflecting half mirror (4) is identical with curved reflector (5) structure, is a kind of by CO ₂the paraboloidal mirror that the material of laser-light transparent is made; Described curved surface half-reflecting half mirror (4) surface is coated with part reflective semitransparent film, and described curved surface half-reflecting half mirror (4) bore is greater than the diameter carrying out the directional light expanded through beam expander (7); Described curved reflector (5) surface is coated with high-reflecting film.

4. method for making according to claim 1, is characterized in that, in step 4, baking condition is: toast 1min at 100 DEG C.

5. method for making according to claim 1, it is characterized in that, described curved surface half-reflecting half mirror (4) has four kinds with the modes of emplacement of curved reflector (5), is respectively: first inside surface (9) of described curved surface half-reflecting half mirror (4) is simultaneously relative with the ellipsoid (2) of source-collector mirror (1) with the second inside surface (9 ') of curved reflector (5); First outside surface (10) of described curved surface half-reflecting half mirror (4) is simultaneously relative with the ellipsoid (2) of source-collector mirror (1) with the second outside surface (10 ') of curved reflector (5); First inside surface (9) of described curved surface half-reflecting half mirror (4) is simultaneously relative with the ellipsoid (2) of source-collector mirror (1) with the second outside surface (10 ') of curved reflector (5); First outside surface (10) of described curved surface half-reflecting half mirror (4) is simultaneously relative with the ellipsoid (2) of source-collector mirror (1) with the second inside surface (9 ') of curved reflector (5).

6. method for making according to claim 1, is characterized in that, described exposure light source (6) adopts CO ₂laser instrument, CO ₂optical maser wavelength is 10.6 μm.

7. method for making according to claim 1, is characterized in that, dilute sodium silicate solution selected by described solvent.

8. method for making according to claim 1, is characterized in that, described etching liquid selects rare HNO ₃with the mixed solution of HF.

9. method for making according to claim 1, is characterized in that, described extreme ultraviolet reflectance coating is Mo/Si multilayer film, cycle 6.9nm, is made up of 40 ~ 50 cycles.

10. method for making according to claim 1, it is characterized in that, also comprise step 9, detection: set A, B as two points on the ellipsoid (2) of source-collector mirror (1), its mid point A is positioned at through hole (8) center, and be positioned at the intersection of primary optical axis (3) and ellipsoid (2), point B is on ellipsoid (2), and some A does not overlap with some B;

When the ellipsoid (2) of source-collector mirror (1) has suitable half-wave zone structure, source-collector mirror (1) is by infrared light refocusing, thus realize the spectrum purifying function at intermediate focus IF place, therefore, half-wave zone structure should be made to meet the reflector space of infrared light: path with path optical path difference be the odd-multiple of the half-wavelength of the laser that exposure light source (6) exports, shown in (1):

$\begin{array}{cc}\stackrel{\‾}{F_1{\mathrm{BF}}_1}-\stackrel{\‾}{F_1{\mathrm{AF}}_1}=(2n+1)\mathrm{\λ}& \backslash *MERGEFORMAT\end{array}---\left(1\right)$

In formula (1), F ₁for the first focus of the ellipsoid at ellipsoid (2) place of source-collector mirror (1), λ is the optical maser wavelength that exposure light source (6) exports, and n is natural number;

Two coherent point light sources lay respectively at the first focal point F ₁with the second focal point F ₂, two coherent point light sources form interference fringe on ellipsoid (2), and wherein bright fringes meets: path with path optical path difference be the integral multiple of the wavelength of the laser that exposure light source (6) exports, shown in (2):

$\begin{array}{cc}\stackrel{\‾}{F_{2}B}-\stackrel{\‾}{F_{1}B}=m\mathrm{\λ}& \backslash *MERGEFORMAT\end{array}---\left(2\right)$

In formula (2), F ₂for the second focus of the ellipsoid at ellipsoid (2) place of source-collector mirror (1), be also the intermediate focus IF of exposure light source (6) output terminal, λ be the optical maser wavelength that exposure light source (6) exports, m is natural number.

In the ellipsoid at ellipsoid (2) place of source-collector mirror (1), there is following geometric relationship: on the ellipsoid at ellipsoid (2) place of source-collector mirror (1) o'clock to the first focal point F ₁, the second focal point F ₂the major axis of distance sum to be constant 2a, a the be ellipsoid at ellipsoid (2) place of source-collector mirror (1) long, shown in (3):

$\begin{array}{cc}\stackrel{\‾}{F_{1}B}+\stackrel{\‾}{F_{2}B}=2a& \backslash *MERGEFORMAT\end{array}---\left(3\right)$

In addition, also exist such as formula the relational expression shown in (4):

$\begin{array}{cc}\stackrel{\‾}{F_{1}A}=a-f& \backslash *MERGEFORMAT\end{array}---\left(4\right)$

In formula (4), f is the focal length of the ellipsoid at ellipsoid (2) place of source-collector mirror (1);

Can be drawn by formula (1), formula (2), formula (3) and formula (4):

$\begin{array}{cc}\begin{array}{c}{\stackrel{\‾}{F_{1}BF}}_1-{\stackrel{\‾}{F_{1}AF}}_1=2\stackrel{\‾}{F_{1}B}\mathrm{-2}\stackrel{\‾}{F_{1}A}\\ =(2a-m\mathrm{\λ})-2(a-f)\\ =2f-m\mathrm{\λ}\end{array}& \backslash *MERGEFORMAT\end{array}---\left(5\right)$

Focal length due to the ellipsoid at ellipsoid (2) place of described source-collector mirror (1) is the odd-multiple of the optical maser wavelength 1/4th that exposure light source (6) exports, that is:

$\begin{array}{cc}f=(2l+1)\frac{\mathrm{\λ}}{4}& \backslash *MERGEFORMAT\end{array}---\left(6\right)$

In formula (6), f is the focal length of the ellipsoid at ellipsoid (2) place of source-collector mirror (1), and λ is the optical maser wavelength that exposure light source (6) exports, and l is natural number;

Then can be drawn by formula (5) and formula (6):

$\begin{array}{cc}\stackrel{\‾}{F_1{\mathrm{BF}}_1}-\stackrel{\‾}{F_1{\mathrm{AF}}_1}=\left(2\right(l-m)+1)\mathrm{\λ}& \backslash *MERGEFORMAT\end{array}---\left(7\right)$

By the first focal point F in the ellipsoid at ellipsoid (2) place of described source-collector mirror (1) ₁, the second focal point F ₂and the triangle Δ F that the some B on ellipsoid (2) is formed ₁bF ₂in i.e. 2l+1 > 2m;

In sum, two coherent point light sources are utilized to interfere the candy strip of the upper structure of the ellipsoid (2) in source-collector mirror (1) consistent with required half-wave zone structure plan.